This invention relates to an electric shift apparatus especially suited for use with a motor vehicle having an automatic transmission.
Motor vehicles since their inception have required some manner of gear change mechanism to satisfy the varying torque and speed requirements encountered during the typical duty cycle of a motor vehicle. For many years these gear change mechanisms were manual in the sense that they required an operator input from a shift lever or the like to effect each desired gear change ratio. More recently, so called "automatic" transmissions have become popular in which much of the shifting is done without operator input in response to sensed speed and throttle opening parameters. These automatic transmissions typically include a mode select member on the transmission housing movable between a plurality of selected positions corresponding to a respective plurality of shift modes within the transmission. The mode select member is moved between its several shift positions by a cable or linkage mechanism extending from the mode select member to a suitable gear selector lever located in the passenger compartment of the vehicle. Various proposals have been made in the past to eliminate the mechanical interconnection between the driver operated lever and the mode select member and provide instead an electrical signal generated by a suitable action on the part of the driver and transmitted electrically to some manner of power means arranged to move the mode select member. None of these attempts to provide an electric shift mechanism for an automatic transmission of a motor vehicle have met with any degree of commercial success since they provided a slow or imprecise shifting action, have added significantly to the cost of the vehicle, or have generated excessive warranty and maintenance costs.